Electromagnetic method of sheet feed control and control devices



March 7, 1961 w. STOLK ELECTROMAGNETIC METHOD OF SHEET FEED CONTROL AND CONTROL DEVICES 2 Sheets-Sheet 1 Filed Oct. 24, 1958 IN VEN TOR.

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VII/)2 a March 7, 1961 w TOLK 2,973,959

. S ELECTROMAGNETIC METHOD OF SHEET FEED CONTROL AND CONTROL DEVICES Filed Oct. 24, 1958 2 Sheets-Sheet 2 IN V EN TOR.

ELECTRQMAGNETIC METHOD OF SHEET FEED CONTROL AND CONTROL DEVICES William Stoih, Lansing, Mich, assignor to Machine Tool Electric Corporation, Lansing, Mich., a corporation of Michigan Filed on. 24, 1958, SerrNo. 759,332

Claims. 01. 271-18) The present invention relates to an improved method of controlling the feed of sheet steel or other ferrous sheets into punch presses or like equipment performing operations in which it is imperative that only a single sheet be so fed, and to devices forperforming the method. The invention makes it possible, by utilizing combined repulsive and tractive phenomena, to separate the top sheet of a stack from the next lower sheet in instances where there is a tendency for these sheets to stick together, by reason of having a coating of grease, a micro-polish finish, and the like.

My copending application, Serial No. 769,328, filed October 24, 1958, has as its subject matter a method and apparatus by which the same general objective is attained in a different manner, relying on an electromagnetic progressive sheet peeling action.

It is an object of the invention to provide an improved electromagnetic sheet feeding method and device for the above purpose, in which a fanning electromagnet is positioned adjacent to the side of a stack of sheets from which the topmost sheet is to be fed, this magnet when energized producing two phenomena resulting in the forwarding of the topmost sheet in the intended direction.

First, the magnetic field of the energized magnet magnetizes the sheets of the stack with the same polarity, causing adjacent successive sheets to repel and tend to separate in the vertical sense. Second, the poles of the magnet exert a force on the topmost sheet in the plane thereof and in the direction of intended advance so that, as the stack is elevated by a rising table, the topmost sheet is drawn in the direction of advance and slides over the top of the electromagnet poles.

Another object of the invention is to provide an electromagnetic fanning type of sheet feed method and device, in which the electromagnetic poles adjacent the side of the stack are equipped with a spacer of nonmagnetic material, over the top of which the advancing sheet slides under the magnetic force referred to above. Inso sliding, it is subject to a downward component of magnetic force which holds the sheet therebeneath from similarly rising and sliding over the non-magnetic spacer and magnet poles.

A further object of the invention is to provide a method and apparatus as described, in which the advancing topmost sheet is employed to trip a limit switch. This switch signal may be employed to de-energize the coil of the electromagnet, or ito bring into play other machinery which will complete the feed of the top sheet, as to another station, or it may halt further upward movement of the stack elevating table, or it may initiate any combination of these actions.

The foregoing as well as other objects will become more apparent as this description proceeds, especially when considered in connection with the accompanying,

drawings illustrating the invention, wherein:

Fig. 1 is a top planview, schematic in nature, of a, simple device for performing an electromagnetic fanning type of feed operation according to the invention;'

atent ice j i Fig. 2 is a fragmentary view, partially broken away and in vertical section, along a line corresponding to line 22 of Fig. 1, showing an initial phase in the fanning and sheet separating operation;

Figs. 3 and 4 are fragmentary sectional views similar to Fig. 2, illustrating succeeding phases, though performed practically instantaneously in thel operation;

Fig. 5 is a sectional view in enlarged scale depicting vector components of the electromagnetic force which are in play;

Fig. 6 is a fragmentary perspective view schematically depicting the repelling effect of magnetic fields of the same polarity on adjacent sheets of the vertical stack;

Fig. 7 is a schematic view showing a general proposed arrangement of eiectromagnet'ic fanning device, sheet elevating table and controls therefor; and V Fig. 8 is a schematic wiring device for the equipment.

Referring first to Figs. 1 through 6 of, the drawings, the reference numeral 10 generally designates an electromagnetic sheet feeding device incorporating the principle of sheet separating and advancing by electromagnetic fanning. This device includes a flat table 11 upon which a stack of sheets 12, 13, 14, etc. are supported, the table being equipped with suitable provisions (hereinafter generally referred to) for elevating the same, preferably in timed relation to the operation of a punch press or like mechanism (not shown) or an auxiliary sheet feeding device (also not shown), by which the topmost sheet 12 of the stack, as separated and advanced by the device 1-0, is fed further to the operating mechanism in question. or to another station.

The reference numeral 15 generally designates an electromagnet suitably wired, asshown in the wiring diagram of Fig. 8, for control of its 'energization in a manner to be described. Electromagnet 15 includes a coil 16 and pole pieces '17 whose inturned faces 18 are located adjacent the side or edge of the stack toward which topmost sheet 12 is to be fed. The pole piece faces 18 are provided with a strip 19 of a suitable non-magnetic material, for a purpose to be described. Appropriate means, not germane to the invention, are provided to fixedly mount the electromagnet 15 in the relation to the stack of sheets which is shown in Figs. 2, 3 and 4 of the drawings. I

A suitable limit switch 20 is also appropriately mounted to position its operating finger '21 for actuation by the topmost sheet 12 as it is separated from the remaining sheets 13, 14, etc., and advanced by the device 10. Elec tromagnet 20 is also wired appropriately in the control circuit, as shown in Fig. 9.

In the operation of the device 10, and with electrov magnet 15 energized and the "table 11 operated to elevate the stack of sheets, 'electromagnet "fields of likepolarity are created in the sheets of the stack, as depicted in Fig. 6 of the drawings. These fields set up repulsive forces in the sheets tending to separate the same vertically, as shown.

As table 11 elevates the stack to bring its topmost sheet 12 above the adjacent top edge of non-magnetic spacer 19, the electromagnetic forces F F shown in Fig. 5, come into play. The force F is in the plane of the sheet 12 and in the intended direction of advance, and the force F may 'be considered to be in the direction of the vertical center of electromagne't pole piece faces 18. The horizontal and vertical vector components of these forces are indicated, although not accurately as to intensity, by the dotted line arrows of Fig. 5.

' It is to be understood that Figs. '2, 3 and 4.01: the

tion of Fig. 2, the magnetic pull in the direction F (Fig. 5), draws. sheet 12 above and over the non-magnetic spacer 19, to the position shown in Fig. 3, and the vertical component of the pull in the direction F draws sheet 12 downwardly onto the spacer 19, thereby preventing the next adjacent sheet 13 from sliding over the spacer, as shown in Fig. 3.

In so advancing the forward edge of sheet 12 sufiiciently to engage and trip the operating finger 21 of limit switch 20 (as shown in Fig. 3), the resultant signal may be employed to (a) Bring into play machinery (not shown) which will cause the sliding of the sheet 12 to another station, for example in the opposite direction indicated by an arrow in Fig. 4;

(b) Halt further upward movement of the table;

(c) De-energize the fanning electromagnet 15, thus allowing all sheets except top sheet 12 to fall back to originally stacked position; or

(d) A combination to these effects.

Fig. 7 of the drawings shows a schematic arrange ment of basic operating and control instrumentalities contemplated by the invention. Thus, the fanning device 15 may comprise a suitable plate-like support 23 upon which the magnet 16 and limit switch 20 are mounted in predetermined lateral and vertical relation to the sheet elevating table 11. The latter may be powered for its elevating movement by a hydraulic ram unit 24, to the plunger to which the table 11 is connected.

The reference numeral 26 designates a suitable solenoid operated hydraulic valve, having connected liquid supply and discharge lines 27, 28, with further hydraulic lines 29, 30 which are equipped with appropriate flow control devices 32 connecting the valve 26 with the ram unit 24, in a manner which will be understood by those skilled in the art. The reference numeral 26' designates an electrical solenoid governing the action of valve 26.

Referring to the wiring diagram of Fig. 8, the schematically illustrated electromagnet 16 is connected in series with the normally closed contact 33 of a control relay 34 across direct current leads 35, 36. These are supplied with a DC. voltage by a rectifier 37. The input leads 38, 39 of the rectifier 37 are connected across a pair of 115 volt alternating current supply leads 40, 41, respectively.

The coil of control relay 34 is connected in series with the terminals of limit switch 20, and a normally closed relay contact 42 across the alternating current leads 40, 41; and a second contact 43 of the control relay 34 is connected in shunt relation to limit switch 20 from the lead 40 to a common terminal of switch 20 and relay contact 42.

When the limit switch 20 is closed by engagement of the top sheet 12 with its operating finger 21, as shown in Fig. 7, the relay 34 is energized, opening its first contact 33 and de-energizing coil 16 of the electromagnet. The normally open contact 43 of relay 34 is closed and current continues to flow through the relay contact 42, which may be employed to energize the solenoid 26 for a further operation of ram unit 24 to elevate table 11, once the topmost sheet 12 has been removed to reopen limit switch 20.

It is seen that the invention affords electromagnetic sheet separating and feeding mechanism performing an improved method featuring a progressive separation of a topmost sheet from a stack of sheets under the infiuence of forces which are entirely electromagnetic. The equipment employed in performing the method is simple and inexpensive, as well as unfailing in operation. It is to be understood that the thickness or weight of the sheets handled, their metallurgical composition, etc. will be determinative of various mechanical and electrical operating adjustments.

What I claim as my invention is:

l. A method of electromagnetically separating stacked sheets and feeding the topmost thereof in the direction of its plane, comprising the steps of horizontally restraining the stack up to a predetermined level along a leading side thereof which is toward said direction of the de sired feed, while creating a fixed electromagnetic field at said side effective from the direction of said restraint to urge said topmost sheet in said first named direction as well as downwardly, and elevating said stack to bring said topmost sheet above said predetermined level of horizontal restraint for advance in said direction under the influence of said magnetic field, while causing said advancing topmost sheet to maintain the sheet therebeneath below said level under the downward effect of said field.

2. A method of electromagnetically separating stacked sheets, comprising setting up in at least the topmost sheet of a stack electromagnetic forces from a single fixed source having the effect of repelling the sheets relative to one another in the direction in which they are stacked, simultaneously subjecting at least the topmost sheet of the stack to an electromagnetic force from said source in a manner causing said last named force to act on and tend to advance said topmost sheet in the direction of its plane, while restraining said advance, and removing the restraint to cause the topmost sheet to be advanced longitudinally under the effect of the force.

3. Apparatus for electromagnetically separating stacked sheets and feeding the topmost thereof, comprising means engageable with a side surface of the stack to restrain the sheets of the same from horizontal movement, fixed electromagnet means on the side of said restraining means opposite said stack energizable to set up electromagnetic forces tending to repel and separate at least the topmost sheets of the stack vertically relative to one another and to urge said topmost sheet horizontally, and means to cause the topmost sheet to be periodically released from horizontal restraint by said first named means whereby the topmost sheet, when released from restraint by said first named means, is horizontally advanced.

4. Apparatus for electromagnetically separating stacked sheets and feeding the topmost thereof, comprising means engageable with a side surface of the stack to restrain the sheets of the same from horizontal movement, fixed electromagnet means on the side of said restraining means opposite said stack energizable to set up electromagnetic forces tending to repel and separate at least the topmost sheets of the stack vertically relative to one another and to urge said topmost sheet horizontally, whereby the topmost sheet, when released from restraint by said first named means, is horizontally advanced, and means to elevate said stack to cause said release.

5. Apparatus for electromagnetically separating stacked sheets and feeding the topmost thereof, comprising means engageable with a side surface of the stack to restrain the sheets of the same from horizontal movement, fixed electromagnet means on the side of said restraining means opposite said stack energizable to set up electromagnetic forces tending to repel and separate at least the topmost sheets of the stack vertically relative to one another and to urge said topmost sheet horizontally, whereby the topmost sheet, when released from restraint by said first named means, is horizontally advanced, and means to cause said release by effecting relative movement of said topmost sheet and said restraining means.

6. Apparatus for electromagnetically separating stacked sheets and feeding the topmost thereof, comprising means engageable with a side surface of the stack to restrain the sheets of the same from horizontal movement, fixed electromagnet means on the side of said restraining means opposite said stack energizable to set up electromagnetic forces tending to repel and separate at least the topmost sheets of the stack vertically relative to one another and to urge the top sheet thereof horizontally, whereby said top sheet, when released from restraint by said. first named means, is horizontally advanced, and means to cause. said release by efiecting relative movement of said top sheet and said restraining means, comprising an elevating table to support the stack having means for operating the same vertically in timed relationto energization of said electromagnet means.

7. A method of electromagnetically separating stacked sheets and feeding the topmost thereof in the direction of its plane, comprising the steps of horizontally restraining the stack up to a predetermined level along a leading side thereof which is toward said direction of the desired feed, while creating a fixed electromagnetic field at said side effective from the direction of said restraint to urge said topmost sheet in said first named direction, and elevating said stack to bring said topmost sheet above said predetermined level of horizontal restraint and to advance in said direction under the influence of said magnetic field, while causing the elevated sheet, as so advanced, to restrain from above the sheet therebeneath against similar advance.

8. A method of electromagnetically separating stacked sheets, comprising providing a horizontally restrained stack of sheets, setting up in said sheets electromagnetic forces "having the effect of repelling the sheets relative to one another in the direction in which they are stacked, and simultaneously causing the topmost sheet of the stack to be freed of said restraint and to be subjected to an electromagnetic force acting on, and tending to advance, the same in the direction of its plane, thereby causing said sheets to be simultaneously separated from one another by the repulsive force and the topmost sheet, as thus repelled and released from horizontal restraint, to be advanced longitudinally of its plane.

9. A method of electromagnetically separating stacked sheets and feeding the topmost thereof in the direction of its plane, comprising the steps of horizontally restraining the stack up to a predetermined level along a leading side thereof which is toward said direction of the desired feed, while creating a fixed electromagnetic field at said side effective from the direction of said restraint to urge said topmost sheet in said first named direction, elevating said stack to bring said topmost sheet above said predetermined level of horizontal restraint and to advance in said direction under the influence of said magnetic field, while causing the elevated sheet, as so advanced, to restrain from above the sheet therebeneath against similar advance, and causing said elevated and advanced sheet to initiate a control action in advancing.

10. A method of electromagnetically separating stacked sheets, comprising providing a horizontally restrained stack of sheets, setting up in said sheets electromagnetic forces having the effect of repelling the sheets relative to one another in the direction in which they are stacked, simultaneously causing the topmost sheet of the stack to be freed of said restraint and to be subjected to an electromagnetic force acting on, and tending to advance, the same in the direction of its plane, thereby causing said sheets to be simultaneously separated from one another by the repulsive force and the topmost sheet, as thus repelled and released from horizontal restraint, to be advanced longitudinally of its plane, and causing said topmost sheet, as thus advanced, to initiate a control action.

References Cited in the file of this patent UNITED STATES PATENTS 1,716,602 Ross June 11, 1929 1,847,139 Seaholm et al. Mar. 1, 1932 2,495,490 Whitson Jan. 24, 1950 2,541,985 Chatterton Feb. 20, 1951 2,650,092 Wall Aug. 25, 1953 2,650,824 Fowler Sept. 1, 1953 

